Announced during the Pokémon Presents broadcast on August 8th, 2023, Paldea region Pokémon will be added to the game in September 2023.

Pokémon first discovered in the Paldea region are coming to Pokémon GO!

Trainers,
A new adventure is on the horizon! Get ready to encounter even more Pokémon on your journey!

Pokémon originally discovered in the Paldea region of the Pokémon Scarlet and Pokémon Violet games for Nintendo Switch are coming to Pokémon GO starting this September.

Stay tuned for more details!

Source: https://pokemongolive.com/en/post/paldea-region-pokemon-announcement/

YouTube Clip - Pokémon first discovered in the Paldea region are coming to Pokémon GO!

Source: https://www.youtube.com/watch?v=sJ5-jc4KZTA